1. Field of the Invention
The present invention relates to an image-reading apparatus reading an image of an original.
2. Description of the Related Art
Hitherto, some image-reading apparatuses such as a copying machine, a scanner, and a facsimile machine include an image-reading section and an original-transporting section transporting an original to the image-reading section. Also, some of the original-transporting sections are capable of opening and closing relative to the image-reading section.
In such an image-reading apparatus, in the case of reading an image of an original placed on a platen glass-plate, that is, in the case of so-called stationery reading, the original is read while moving an image-reading mechanism provided in the image-reading section in a sub-scanning direction. Whereas, in the case of reading an image of an original transported over the platen glass-plate by the original-transporting section, that is, in the case of so-called skimming, the image-reading mechanism is moved to a predetermined reading position so as to read the image of the original at the predetermined position.
Such an image-reading apparatus includes an automatic document feeder (herein after, referred to as ADF) having functions, e.g., separating a plurality of originals (sheets) sheet by sheet placed on an original-placing plate, transporting the original sheet to a predetermined image-reading section, and reading the original sheet at the image-reading section, in addition to flipping its front and back sides from each other and discharging it.
FIG. 7 is a sectional view of the structure of an example known image-reading apparatus. The image-reading apparatus mainly includes an ADF 100 and a reader section 200 constituting the image-reading section. The reader section 200 has a platen glass-plate 202 disposed on the upper surface of a main body 1 of the image-reading apparatus and a reading mover 201 provided therein, serving as an image-reading mechanism and including a light source 204, a first mirror 206, and so forth. The image-reading apparatus has a first reading mode (a stationery reading mode) and a second reading mode (a skimming mode). In the first reading mode, an original set by an operator on the platen glass-plate 202 is read by moving the reading mover 201 in an arrow direction indicated in the figure. In the second reading mode, the reading mover 201 is halted at a predetermined position, and an original set on the ADF 100 is read while transported over the platen glass-plate.
In the second reading mode in which the ADF 100 constituting the original-transporting section is used, after skew of the original is corrected by pushing its front end into contact with a regist roller pair 1101 (1101a and 1101b) and making a loop of the original, an image of the original (hereinafter, sometimes referred to as an original image) is read by transporting the original to a reading position 102 with a lead roller pair 1103 (1103a, 1103b).
In the second reading mode, on the occasion of reading the original image as described above, reading accuracy of the image depends on respective positional accuracy of the resist and lead roller pairs 1101 and 1103.
In other words, when the axial line of the nip of the regist roller pair 1101 is at an angle relative to the optical axis, extending in a widthwise direction, i.e., perpendicularly to the moving direction of the reading mover 201, of (the light source 204 of) the reader section 200, skew compensation of the original is unsatisfactory. When the skew compensation of the original is unsatisfactory as described above, the original image is not accurately read. As a result, an image formed on a sheet on the basis of reading information of the original image is skewed as shown in FIG. 8A. Hereinafter, such a problem is called poor skew alignment.
When the axial line of the nip of the lead roller pair 1103 is at an angle relative to the optical axis, the original cannot be transported to the reading position 102 orthogonally relative to the optical axis. In such a case, since the image is not accurately read, an image formed on a sheet on the basis of reading information of the original image is skewed in a widthwise direction as shown in FIG. 8B. Hereinafter, such a problem is called poor orthogonal alignment.
When such a problem, e.g., poor skew alignment occurs, the position of the idle-side regist roller 1101 contacting with the drive-side regist roller 1101a is adjusted as a skew adjustment so that the axial line of the nip of the regist roller pair 1101 agrees with the optical axis of the reader section 200.
When poor orthogonal alignment occurs, by adjusting the position of a hinge (not shown) integrally and rotatably supporting the reader section 200 and the ADF 100 on the far side from the observer in the figure, the position of the ADF 100 relative to the reader section 200 is adjusted as an orthogonal adjustment so that the axial line of the nip of the lead roller pair 1103 agrees with the optical axis.
FIG. 9 is a sectional view of the structure of another example known image-reading apparatus. The image-reading apparatus mainly includes an ADF 600 and a reader section 700. The reader section 700 has a platen glass-plate 702 disposed on the upper surface of a main body 2 of the image-reading apparatus in addition to having a reading mover 701, a light source 704, a first mirror 706, and so forth provided therein. The image-reading apparatus has first and second reading modes. In the first reading mode, an original set by an operator on the platen glass-plate 702 is read by moving the reading mover 701 in an arrow direction indicated in the figure. In the second reading mode, the reading mover 701 is halted at a predetermined position, and an original set on the ADF 600 is read while being transported over the platen glass-plate.
In the second reading mode in which the ADF 600 is used, after skew of the original is corrected by pushing it into contact with a regist roller pair 1601 (1601a and 1601b) and making a loop of the original, an original image is read by transporting the original to a reading position 602 with a transporting belt 603.
On the occasion of reading the original image as described above, reading accuracy of the image mainly depends on the respective positional accuracy of the regist roller pair 1601 and a stretching roller 1604 stretching the transporting belt 603 together with an idle roller 1605.
In other words, when the axial line of the nip of the regist roller pair 1601 is at an angle relative to the optical axis, extending in a widthwise direction, i.e., perpendicularly to the moving direction of the reading mover 701, of (the light source 704 of) the reader section 700, skew compensation of the original is unsatisfactory, resulting in poor skew alignment of the original. When the axial line of the stretching roller 1604 stretching the transporting belt 604 is at an angle relative to the optical axis, the original cannot be orthogonally transported to the reading position 602 relative to the optical axis, resulting in poor orthogonal alignment.
For example, when poor skew alignment occurs, the position of the idle-side regist roller 1601b contacting with the drive-side regist roller 1601a is adjusted as a skew adjustment so that the axial line of the nip of the regist roller pair 1601 agrees with the optical axis of the reader section 700. When poor orthogonal alignment occurs, by adjusting the position of a hinge (not shown) integrally and rotatably supporting the reader section 700 and the ADF 600 on the far side from the observer in the figure, the position of the ADF relative to the reader section 700 is adjusted as an orthogonal adjustment so that the axial line of the stretching roller 1604 agrees with the optical axis.
Mutually independently performing the skew adjustment and the orthogonal adjustment as described above requires much time and increases the number of adjusting steps. In view of this, for example, image-reading apparatuses disclosed in Japanese Patent Laid-Open No. 10-142851 (corresponding to U.S. Pat. No. 6,027,109) have structures in which, by forming a paper-feeding section, a transporting section, and a paper-discharging section of the ADF 100 or 600 as a single unit and by arranging a projection formed on the unit so as to abut against the upper surface of the platen glass-plate of the reading section 200 or 700, the unit is positioned in the vertical direction relative to the reading section 200 or 700 such that the number of adjusting steps needed upon installing the reading section 200 or 700 to the ADF 100 or 600, respectively, is reduced.
Unfortunately, in such known image-reading apparatuses, although the number of steps needed upon installing the ADF 100 or 600 on the corresponding reading section 200 or 700 is reduced, the skew adjustment and the orthogonal adjustment are still needed.
In the case where the unit including the paper-feeding section, the transporting section, and the paper-discharging section is vertically positioned with the projection serving as a positioning section, a variety of original-transporting sections are needed to undergo an alignment adjustment relative to the positioning section. In the case where the frame of the ADF 100 or 600 is deformed, for example, due to use of the apparatus, even when the plurality of original-transporting sections are subjected to the alignment adjustment relative to the positioning section of the unit, the alignment causes the plurality of original-transporting sections to misalign relative to the positioning section of the unit, and no way is prepared for correcting the misalignment. As a result, the original transported by the ADF 100 or 600 is at an angle relative to the optical axis of the reader section 200 or 700, respectively.
An image-reading apparatus disclosed in Japanese Patent Laid-Open No. 08-223362 has a cover capable of opening and closing relative to the main body thereof. The cover has a read roller rotatably provided thereon. The axis of the read roller is positioned in an original-transporting direction with a positioning mechanism provided in the main body of the image-reading apparatus. The read roller positioned by the positioning mechanism is pressed into contact with a contact glass or a contact sensor provided in the main body of the image-reading apparatus. Accordingly, even if the read roller is satisfactorily positioned, when the original is sent to the contact sensor in a state in which it is already skewed at the upstream of the read roller, an image of the original is read in a skewed state. As a result, the image of the original is not accurately read. Hence, an additional adjustment is needed so that the original is sent to the contact sensor without skew.